Torsional vibration damper having two part hub

ABSTRACT

A torsional vibration damper and method and apparatus for its manufacture. The outer inertia member carries a radially inwardly extending web, the web sandwiched by a pair of elastomer members. A two-piece hub sandwiches the elastomer members, the two hub pieces being held together as by swaging or by rivets. Tooling for the swaging mode of assembly is shown such that the elastomer members are deformed from an original to a final configuration, and the swaging then accomplished with a single continuous movement. The swaging assembly apparatus for the device includes Belleville springs, the apparatus limiting the maximum force applied to that portion of the hub members controlling the assembled elastomer thickness. The damper configuration facilitates low specific energy dissipation and large elastomer-to-metal interface area to thus tend to lower shear stress in the elastomer. In addition, should the elastomer fail in use, the damper inertia mass is mechanically constrained to remain with the hub assembly. The two hub pieces cause radial extrusion of the elastomer, the extruded portions contacting the inertia member, the latter guiding and defining the extrusions.

This invention relates to torsional vibration dampers of the typeemployed in internal combustion engines. Such dampers find wideapplication in internal combustion engines for automobiles, as well asthe diesel engines commonly employed in the trucking industry.

The crankshaft of an internal combustion engine is subject to torsionalvibrations. Such vibrations arise from the sequential explosion ofcombustible gases in the several cylinders. After one cylinder has fireda certain length of time elapses before the firing of another cylinder.The application of forces of rotation to the crankshaft of an engine isaccordingly not smooth and continuous. Only if the number of cylinderswere nearly indefinitely increased would such torsional vibrations besubstantially eliminated. While the crankshaft is turning at, forexample, 3000 rpm, delivering power to the wheels of the vehicle, it isexecuting torsional oscillations of, for example, one-fourth of onedegree twist between the flywheel and the front pulleys at a frequencyof 150-250 cycles per second. In certain cases, the natural frequency oftorsional vibration of the crankshaft may coincide with a particularfiring frequency or harmonic of that frequency with the result thatresonance may be amplified. Such an action causes appreciable strains inthe crankshaft and may result in immediate failure or lead ultimately toits fatigue failure.

For a long number of years, workers in this art have recognized thisproblem and have constructed a variety of devices to lessen suchtorsional vibrations. One common form of torsional vibration damper isthat defined by a hub coupled to the crankshaft either directly orindirectly. The hub carries an elastomer element around its rim, and theelastomer element is, in turn, coupled to an outermost annular member.This outermost annular member is often termed the inertia member. In thecase of torsional vibration, the hub executes such vibrations in phasewith the crankshaft because it is rigidly coupled to it. The inertiamember is coupled to the hub by the elastomer and accordingly there is aphase lag between the oscillations of the hub and the correspondingoscillations of the inertia member. In the case of a vibration damper ofthis type, a portion of the energy of the torsional vibrations would betransformed into heat in the elastomer member and thereby dissipated.The heat arises in the elastomer member by virtue of internal ormolecular friction within it. The phase difference between the inertiamember and the hub member stretches or deforms the elastomer, suchmechanical perturbation being resisted by intermolecular forces of bothconservative and non-conservative nature.

For a given damper application, i.e., a damper for a specific engine, itis known in the art to use as much elastomer (volumewise) with as muchshear area (interface area between metal and elastomer) as possible tominimize both the power absorbed per unit of volume and also to minimizeshear stress. In practice, space limitations preclude simply expandingthe width or the diameter of the damper to achieve these low values.

The practice of this invention facilitates the design of torsionalvibration dampers having these desirable properties within given spacelimitations. The damper of this invention also exhibits high radial andaxial stiffness. The invention further comprehends a desirable assemblyapparatus for constructing those modifications of the invention whichutilize metal deformation, such as swaging, to hold the damper elementsin their assembled relation.

In the drawings:

FIG. 1 is a longitudinal axial cross-section of a torsional vibrationdamper of this invention.

FIG. 2 is a longitudinal cross-section of an apparatus for assemblingthe damper of FIG. 1, and illustrates the mode of assembly at theinitial stage of damper assembly.

FIGS. 3-6 are similar to FIG. 2 and illustrate various stages of damperassembly.

FIG. 7 is a chart containing certain curves which illustrate the mode ofassembly of FIGS. 2-6.

FIG. 8 is a view similar to FIG. 1, and illustrates an embodiment.

FIGS. 9-11 illustrate another embodiment of the damper of thisinvention, as well as another assembly apparatus.

FIG. 12 is a view similar to FIG. 1 and illustrates still anotherembodiment.

Referring now to the damper shown at FIG. 1 of the drawings, the numeral10 denotes an outer inertia member in the form of a continuous ring,i.e., an annular member. The numeral 12 denotes an annular and radiallyextending web or tongue extending inwardly from and integral with theinertia member, the web positioned generally midway of the inertiamember's axial extent. The numeral 14 denotes a first elastomer annulusoriginally in the form of a flat disc or washer and now having aradially outermost portion 16 which extends in a generally axialdirection. The numeral 18 denotes a second elastomer annulus, alsooriginally in the form of a flat disc or washer and now having aradially outermost portion 20 also extending in a generally axialdirection. The numeral 24 denotes an annular hub member or piece, thehub including a upper flange portion 26 and a radially innermost sleeveportion 28. A radially extending annular shoulder 30 extends betweensleeve portion 28 and an intermediate annular, axially extending surface31 of the hub. The numeral 34 denotes an annular clamping ring which mayalso be termed a second hub member or piece. Numeral 36 denotes acontinuous annular groove or channel in the inner surface of ring 34,the groove receiving a radially outwardly swaged portion 38 which isintegral with sleeve portion 28, the swaging having taken place by amethod and apparatus described below.

The reader will observe that the web 12 axially locks the inertia member10 relative to the hub 24 and clamping ring 34 and thus precludesrelative axial excursions between these elements. The elastomer membersare maintained compressed (distorted) by the retaining forces afterassembly. If desired for a specific application, an adhesive bond may beprovided between one or both elastomer members and an associatedinterface. It will further be observed that elastomer elements 14 and 18need not be of the same thickness or of the same properties. Thus, onemay be selected for its high resistance to torque and the other for itshigh conversion of rotary oscillations into heat. The inertia and hubmembers are formed of metal, although non-metal materials such as areinforced plastic may be employed.

Referring now to FIGS. 2-6 of the drawings, an apparatus and method forassembling the torsional vibration damper of FIG. 1 will now bedescribed.

The numeral 50 denotes an annular cup having a central aperture 51 and alower face 52. The numeral 56 denotes a movable anvil element ofgenerally annular construction also having a central aperturetherethrough. An outermost radially extending face 58 is carried byanvil 56, the anvil also carrying a radially extending, intermediateface 60 communicating with tapered bore portion 62, the lattercommunicating with an innermost radially extending annular face 63.

The numeral 70 denotes a central stud in the form of a cylinder havingan upper portion 74 of somewhat lesser diameter, the lower or baseportion of 70 denoted by the numeral 72 and being of maximum diameterand stepped. Belleville springs are denoted generally by the numeral 80and extend between base 72 and anvil 56, urging these two members apart.Such springs may be chosen to have the well known property of a nearzero local spring rate after a certain deflection and before the portionwhere no further deflection can take place thereof is attained, as ismore fully shown at a portion of FIG. 7. Anvil 56 is slidable relativeto stud portion 70, as is cup 50. The several elements of the torsionalvibration damper of FIG. 1 are now placed as indicated in the apparatusshown in FIG. 2. For convenience in explaining the action, the attentionof the reader is invited to Scale 1 of each of FIGS. 2-6 which indicatesthe displacement of cup 50 under the influence of some externallyapplied force and also to Scale 2 which indicates the displacement ofanvil 56 against the Belleville springs. The reader will understand thatbase portion 72 is considered fixed or immovable.

Force is applied downwardly, to cup 50. This force may be derived from ahydraulic ram or any other device capable of exerting large forces. AtFIG. 3, the cup 50 has moved downwardly, as may be noted by reference toScale 1, and elastomer discs 14 and 18 commence to deform, with aportion of each being forced radially outwardly and into the spacebetween the two hub portions 24 and 34 and the radially innermostportion of inertia member 10. Belleville springs 80 and annular anvil 56have moved only slightly between the positions shown at FIGS. 2 and 3.At FIG. 4, the deformation of the elastomer discs 14 and 18 is verynearly complete and the reader will observe the formation of axiallyextending portions 16 and 20. The reader will also note at FIG. 4 thatsignificant deflection of Belleville springs 80 has taken place, alongwith attendant motion above them. At FIG. 5, the clamping ring 34 atportion 33 thereof has now contacted radially extending shoulder 30 ofhub 24 and, further, the desired distortion of the elastomer members 14and 18 is complete. Further elastomer compression is restricted bymechanical contact between the two hub members at shoulder 30 of hub 24.That is to say, it is now desired that no further squeezing force beapplied to the two hub members 24 and 34 that would continue withrelative axial motion between the two. In the particular example given,a force of 10 tons is the force required to squeeze the elastomers tothe final desired assembly configuration. A load between the two hubmembers in excess of 10 tons would begin to deform the contact shoulder(30) between the two. However, the desired swaging has not yet takenplace. The Belleville springs have now reached the point in theirload-deflection curve whereby further compression of these springs takesplace without significant additional force.

Continued motion of the cup 50 induced by the ram now causes, in passingfrom the configuration of FIG. 5 to that of FIG. 6, the lower end ofsleeve 28 to abut annular shoulder 76 of stud 70. Such abutment forces aportion of the material of sleeve 28 radially outwardly and into groove36 of clamping ring 34. The portion which so is deformed into the grooveis denoted by the numeral 38 at FIG. 1.

Referring now to FIG. 7 of the drawings, a chart for a particularexample, illustrating the various Load vs. Deflection properties ofseveral of the elements shown at FIGS. 2-6 is illustrated. At FIG. 2,the elements of the damper have just been placed into the assemblyapparatus and no appreciable loads of any sort are present. When thestage indicated at FIG. 3 is reached, the ram load is three (3) tons andthe Belleville springs 80 have deflected approximately 0.04 inches.Similarly, the elastomer elements have undergone an axial deflection ofapproximately 0.16 inches. When the stage indicated at FIG. 4 isarrived, the ram load is nine (9) tons and the Belleville springs havenow been deflected approximately 0.16 inches, and contact betweenportion 33 of locking ring 34 and shoulder 30 of hub 24 is impending.When the configuration of FIG. 5 has been reached, the desired elastomerdeformation corresponding to a force of ten (10) tons has been reachedand no further deformation of the elastomer takes place. Similarly, thecontact between the radially extending faces 33 and 30 has taken placeand swaging has commenced. That is to say, the lower portion of sleeve28 has just contacted rounded shoulder 76 of stud 70. From theconfiguration shown at FIG. 5 to the configuration shown at FIG. 6,swaging has occurred, final swaging taking place at a ram load of 75tons.

Referring now to FIG. 8 of the drawings, another embodiment isillustrated wherein fasteners are employed to hold the two hub portionstogether, instead of swaging or other metal deformation. At FIG. 8, thenumeral 240 indicates a hub portion, similar to hub portion 24 of thepreviously described embodiment. Similarly, clamping ring or second hubportion 340 is shown and corresponds very nearly in structure andfunction to clamping ring 34 of the previously described embodiment. Aplurality of angularly disposed fasteners, such as rivets 90 hold thedamper assembly together. The reader will understand that to fashion themodifications shown at FIG. 8, a cup and anvil similar to cup 50 andanvil 56 of FIGS. 2-6 are employed. After the ram and anvil havesqueezed the assembly to the desired degree, rivets 90 are inserted inpreformed apertures in hub members 240 and 340 to hold them together.

Referring now to FIGS. 9-11, another embodiment of a torsional vibrationdamper formed in accordance with this invention is given. The essentialdifference between the embodiments shown at FIGS. 9-11 and that shown atFIG. 1 is that instead of radially swaging a portion of an inner hubinto a groove on a clamping ring, the corresponding hub portion isoutwardly flared and somewhat clamps the clamping ring. At FIG. 9, thenumerals 10, 14 and 18 denote respectively, the inertia member and thetwo elastomer members. The numeral 24' denotes a hub similar to hub 24of FIG. 1, while the numeral 34' denotes a second hub member or clampingring similar to hub 34 of FIG. 1. Cup 50' carries an annular groove onthe lower face, the groove including an annular surface 100 biased asillustrated. Anvil 56' receives hub 24'. In passing from the initialstage of FIG. 9 to the assembly shown at FIG. 11, the cup 50' is urgedagainst fixed anvil 56', with result that the forward end of sleeveportion 28' abuts surface 100 of the cup, forcing this forward portionradially outwardly and against circumferential biased portion 35 of theclamping ring 34'. A fixture similar to the cup 50' and anvil 56' ofFIG. 9 may be employed to fabricate the modification shown at FIG. 8 ofthe drawings.

In the embodiments of the damper shown in FIGS. 1-11, each annularelastomer element 14, 18 may be considered as comprising a radiallyinnermost portion (not bearing a separate numeral) and a radiallyoutermost portion 16, 20, respectively. Each radially outermost portionextends, in longitudinal axial cross-section, in a generally axialdirection. It will be observed that the elastomer members 14, 18 are incompression in a direction normal to their surfaces which are in contactwith the inertia member and hub.

Referring now to FIG. 12 of the drawings, still another embodiment isillustrated. The outer inertia member is denoted by the numeral 10' andcarries an innermost groove or channel designated by the numeral 11 onits innermost radial surface centrally of the inertia member. Thenumeral 24" denotes one of the two hub pieces and includes a ledge orintermediate portion 31' similar to numeral 31 of the embodiment ofFIG. 1. The other piece of the two-piece hub is denoted by the numeral34", this element functioning as a clamping ring. The numerals 27 and27' denotes the outermost radial portion on the axial faces of each ofelements 34" and 24", respectively. The numeral 15 denotes an elastomerelement which has been axially deformed as in a manner previouslydescribed so that it completely fills the volume between the two hubpieces and the groove 11. Prior to assembly, a typical elastomer for theembodiment of FIG. 12 is in the form of an annular member of rectangularcross-section and having an axial dimension somewhat greater than thedistance between the innermost portions of elements 24" and 34" andhaving a radial dimension approximately equal to that between surface31' and the innermost radial surface of the inertia member 10'. Thereader will immediately comprehend that portions 27 on the hubs form adual function. Firstly, they very nearly completely seal or close theaxial faces of the elastomer and accordingly protect the elastomerwhenever the damper is used in an environment containing gases, forexample, which are harmful to the elastomer. Secondly, they morepositively preclude the squirming of the elastomer out of the damper.The reader will further understand that the embodiment of FIG. 12 neednot include radially extending portions 27 on the two hub elements,rather, the radially outermost portions of the two hub pieces may extendparallel to the axis of rotation of the damper. The embodiment shown atFIG. 12 is assembled in either apparatus such is shown at FIG. 2 or atFIG. 9. During assembly, as is also the case with the damper elementspreviously described, the axial squeezing of the elastomer in an axialdirection results in an extrusion of the elastomer radially outwardly,with very little reduction in the inner diameter of the elastomerbetween its undistorted, initial configuration and its distorted, finalconfiguration. This is true both of the single elastomer embodimentshown at FIG. 12 and the other two elastomer embodiments. In allembodiments, the radially outwardly extruded elastomer is guided by thetwo hub pieces and also contacts a portion of the inertia member. In theembodiment of FIG. 12, it would be apparent that the elastomer whichextends into groove 11 of the inertia member serves to preclude axialexcursion of the inertia member with respect to the hub pieces.

It will further be apparent that the precise configuration of the twohub pieces of this invention may vary for specific design applications.

I claim:
 1. A torsional vibration damper including(a) an annular inertia member, (b) a radially inwardly extending annular tongue carried by the inertia member, (c) a pair of annular elastic members each having a radially innermost portion and a radially outermost portion, (d) said radially innermost portions comprising radially extending portions which sandwich the tongue, (e) a two-piece hub, (f) the two-piece hub sandwiching the tongue and a portion of the elastic members, the said radially outermost portions of the elastic members extending, in a longitudinal axial cross-section, in a generally axial direction and being sandwiched by portions of the hub pieces and portions of the inertia member.
 2. The damper of claim 1 wherein the elastic members are in compression in a direction normal to their surfaces at all points thereof which are in contact with the inertia member and the hub.
 3. The damper of claim 1 wherein the elastic members are adhesively bonded to the said annular tongue.
 4. The damper of claim 1 wherein the elastic members are adhesively bonded to the said two-piece hub.
 5. The damper of claim 1 wherein the elastic members are adhesively bonded to both the said annular tongue and, respectively, to the said two-piece hub.
 6. The damper of claim 1 wherein the two elastic members are of different elastomers, whereby one elastomer is employed for its resistance to torque and the other elastomer is employed for its high conversion of the energy of rotary oscillations into thermal energy.
 7. The damper of claim 1 wherein the two pieces of the said two-piece hub are held together by a deformation on at least one of them.
 8. The damper of claim 1 wherein the two pieces of the said two-piece hub are held together by angularly spaced fasteners.
 9. A torsional vibration damper of the type having an inertia member and a hub, the inertia member and hub joined by at least one radially extending annular elastomer element, the improvement comprising, the hub and inertia ring fastened together and distorting the radially outermost portion of the radially extending elastomer element in an axial direction, the amount and nature of the distortion being such that the radially outermost portion of the elastomer element extends into an axially extending annular space between a radially outermost surface of the hub and a surface of the inertia member to thereby define an axially extending elastomer portion, whereby the elastomer shear interface area between the inertia member and the hub is increased, and whereby the elastomer member is in compression at all points thereof which are in contact with the inertia member and the hub. 